FR3128955A1 - Ferrite material with garnet structure at low sintering temperature and high saturation magnetization for cosintering with silver or gold metallization and process for manufacturing the ferrite material. - Google Patents

Abstract

The subject of the invention is a ferrite material with a garnet structure characterized in that it corresponds to the following chemical formula: (YaTRbBib'FecAldIneCafCugSnhViCojSikO12±γ) + x (Li2CO3 or Li2O or LiF or LiCl) with x, in mass %, between 0.1 and 2; with TR: a rare earth or a combination of rare earths not including the element Y; -1 ≤ γ ≤ 1;3 (a+b+b'+c+d+e) + 2 (f+g+j) + 4 (h+k) + 5 i = 24±2γ;0 ≤ a ≤ 2.5;0 ≤ b ≤ 1.5;0.5 ≤ b' < 3;4 ≤ c ≤ 5;0 ≤ d ≤ 1.5;0 ≤ e ≤ 0.8;0 ≤ f ≤ 1.0 < g ≤ 0.05; 0 < h ≤ 1; 0 ≤ i ≤ 0.8; 0 ≤ j ≤ 0.5; 0 ≤ k ≤ 0.5. The invention also relates to a process for manufacturing the ferrite material of the invention.

Description

Ferrite material with garnet structure at low sintering temperature and high saturation magnetization for cosintering with silver or gold metallization and process for manufacturing the ferrite material.

The field of the invention is that of microwave circulators and isolators. These non-reciprocal devices are used in the case of simultaneous transmission/reception or in isolator mode, in order to protect the source from impedance mismatches.

More specifically, the present invention relates to new materials and their production for integration into microwave circulators/isolators.

There illustrates the diagram of a three-plate circulator made up of 4 main elements:
- the ferrite 10, at the origin of the non-reciprocity of the circulator under the effect of a magnetic field. It can advantageously be a garnet for applications between 1 and 12 GHz;
- the conductive lines 11, which can be gold or silver;
- ground planes 12;
- the permanent magnet 13.

A challenge during the production of such devices, in particular used in electronic active scanning antennas, is the reduction of their cost and their size without degrading their performance.

For this, these devices can advantageously be made by cosintering. This technique allows:
- to reduce the number of steps during the production of the assemblies (in fact, the various elements constituting a circulator are assembled before global sintering) and thus to simplify the production of a circulator in triplaque technology or microstrip line " microstrip " ;
- to get rid of the use of glue which alters the performance of the devices as well as their lifespan.

FIGS. 2a and 2b illustrate for this purpose diagrams respectively of the three-plate and “ microstrip ” microstrip line technologies. There highlights a magnet 13, a central ferrite 10 a Y Junction 11 and a ground plane 12. The highlights a ground plane 12, a ferrite 10 and a Y junction 11.

The process of making these devices is long and expensive and the mechanical assembly of the different elements is complex. In order to simplify this process, adapting the different materials to a cosintering process can be a solution.

In order to cosinter with gold or silver, it is essential to adapt the central material, ferrite, responsible for the non-reciprocal effect of the circulator when subjected to a magnetic field.

A ferrite material particularly well suited to the applications targeted in the present invention and in particular for applications in the frequency range [1 GHz, 12 GHz] is a ferrimagnetic garnet of yttrium iron (YIG).

The metals considered for the production of the co-sintered metal tracks are generally gold and silver, the melting temperatures of these metals being respectively 1064 and 962 °C, it is therefore essential to adapt the sintering temperature of the ferrite. Yttrium iron garnet (YIG) has a high sintering temperature of 1450-1500°C. It cannot therefore be envisaged to box it with gold or silver.

Studies published in patent applications EP1829061A1, EP2622613A1, the thesis of L. Pinier (New ferrimagnetic garnets at low sintering temperature for microwave applications. Doctoral thesis of the Ecole Polytechnique, 2006) and the thesis of L. Qasym (Study and development of ferrites with a garnet structure at low sintering temperature for integration into microwave circulators. Doctoral thesis from the University of Paris Saclay, 2017) have shown that it is possible to sinter garnet ferrites derived from YIG below their initial sintering temperatures. More precisely :
- the Cu-substituted YIG has a sintering temperature lowered to 1050°C;
- the Cu and Bi substituted YIG has a sintering temperature lowered to 950°C;
- the substituted YIG Cu, Bi, V has a sintering temperature lowered to 900°C.

These results are summarized in the following table: Substitution Sintering temperature (°C) Publication Cosinter compatibility Comment At Ag Yttrium iron garnet (YIG) 1450 – 1500 No No Sintering temperature too high YIG substituted Cu 1050 EP1829061A1 EP2622613A1
Th. L. Pinier No No YIG substituted Cu and Bi 950 Yes No YIG substituted Cu, Bi and V < 900 Thesis L. Qasym Yes No Chemical compatibility issue

These first results show that even with sintering temperatures far enough away from the silver melting temperature, cosintering with silver remains complicated. Document FR 3105217, disclosing the results of a study carried out by the Applicant, shows that it is possible to obtain materials at low sintering temperature allowing co-sintering with silver by using lithium carbonate as flux. On the basis of the formulation presented above, is added, after calcination (garnet phase already formed), a carbonate or a lithium oxide serving as flux. This addition makes it possible to reduce the sintering temperature to around 900°C and the cosintering tests show the compatibility of this material with silver.

The addition of lithium carbonate as a flux therefore makes it possible to lower the sintering temperature.

Moreover, for certain applications, such as applications at higher frequencies for example, it is necessary to have saturation magnetizations greater than 180 mT.

• Article de G. Winkler, P. Hansen et P. Holts : Variation of the magnetic material parameters and lattice constants of polycristalline yttrium-iron garnet by incorporation of non-magnetic ions (1972) ;
• Article de Q. Xu et al., Effect of Sn-substitution on the microstructure and magnetic properties of Bi-CVG ferrite with low temperature sintering (2011);
• Article de Y. Machida, Y. Nakayama, H. Saji, T. Yamadaya, et M. Asuma, Magnetic Properties and Resonance Linewidths of Zr- and Ti-Substituted Ca-V Garnet, IEEE Transactions on Magnetics, September 1972.

From classical garnets, a solution to increase the YIG saturation magnetization is the substitution of Fe ³⁺ ions located in octahedral site by 4+ ions, such as Zr ⁴⁺ , Ti ⁴⁺ or Sn ⁴⁺ , disclosed in the following items:

• Article by G. Winkler, P. Hansen and P. Holts: Variation of the magnetic material parameters and lattice constants of polycrystalline yttrium-iron garnet by incorporation of non-magnetic ions (1972);
• Article by Q. Xu et al., Effect of Sn-substitution on the microstructure and magnetic properties of Bi-CVG ferrite with low temperature sintering (2011);
• Article by Y. Machida, Y. Nakayama, H. Saji, T. Yamadaya, and M. Asuma, Magnetic Properties and Resonance Linewidths of Zr- and Ti-Substituted Ca-V Garnet, IEEE Transactions on Magnetics, September 1972.

These materials have lower permittivity.

Moreover, the sintering temperatures presented in these articles are not low enough: 1450°C for the first, 1075°C for the second and 1270-1350°C for the third. These materials with substitution of iron by zirconium, titanium and tin are therefore not compatible for cosintering, neither with silver nor with gold. These solutions run counter to the initial objective of having a sintering temperature below 900°C.

On a similar principle, the Applicant carried out tests with other substitutions of iron by titanium and hafnium. The results were inconclusive. The sintering temperature remains too high and incompatible with cosintering with silver.

Another solution to obtain sufficiently high magnetizations and low sintering temperatures is the substitution of the Fe3+ ion by the Zr4+ ion associated with bismuth/copper substitutions (reference: Thesis Lilia Qassym. Study and development of ferrites of garnet structure at low sintering temperature for integration in microwave circulators. Doctoral thesis from the University of Paris Saclay, 2017). A material is then obtained with Ms (saturation magnetization) between 180 and 200 mT sintering at 950°C. This substitution appears to be the most promising way. Such a material then has a sufficiently high saturation magnetization. On the other hand, its sintering temperature of 950°C remains too high to allow cosintering with silver. Two ways of reducing the sintering temperature can be pursued:
- the use of vanadium as a substitute; Or
- the use of lithium carbonate as a flux.

Due to the high chemical affinity of vanadium oxide and silver oxide at low temperature, the use of vanadium for cosintering with silver metallization has been prohibited. The remaining solution is therefore the use of lithium carbonate on the zirconium substituted material. A study was carried out highlighting the inefficiency of the use of lithium carbonate: if its addition as a flux after chamottage indeed leads to sufficient densification at less than 950°C, it also leads to the appearance of a parasitic phase. disturbing the dielectric (permittivity and dielectric losses) and magnetic properties of the material with a significant reduction in the magnetization at saturation.

Indeed, on the basis of the teachings of the prior art, an addition of lithium carbonate was carried out on the zirconium substituted compositions which fulfill the criterion of magnetization at sufficiently high saturation. Unfortunately, the insertion of lithium into the zirconium substituted lattice is not optimal and, if the density is sufficient at low sintering temperature (at least 95% densification at 900°C), its insertion leads to a non-negligible increase losses and above all the reduction of the saturation magnetization.

The table below presents the saturation magnetization of two materials (zirconium substituted at 0.3 and at 0.5) for an addition of 0, 0.64% and 1.28% by weight of lithium carbonate. It appears that the more lithium carbonate is added, the more the magnetization at saturation decreases. % mass Li ₂ CO ₃ Zr = 0.3 Zr = 0.5 0 190 mT 183 mT 0.64 179 mT 170 mT 1.28 168 mT 155 mT

Thus, it has been demonstrated that it is possible to cosinter new Bi-Cu substituted garnets with gold but also with silver, with a view to reducing costs, thanks to the use of carbonate of melting lithium. But these new materials have a saturation magnetization around 170 mT. However, it has been shown that for higher frequency applications (Ku band for example), it is essential to increase the magnetization of our garnets. A solution resulting from previous studies makes it possible to obtain magnetizations at saturation greater than 180 mT but this material is not compatible with the use of lithium carbonate as a flux (good densification at low sintering temperature but appearance of losses and decrease in saturation magnetization due to the appearance of parasitic phases).

In other words, solutions known from the prior art make it possible to reduce the cosintering temperature of the material. Other known solutions make it possible to increase the saturation magnetization of the material. But these solutions are not mutually compatible. The known prior art therefore does not offer a solution for obtaining a ferrite material with a garnet structure at low sintering temperature and high saturation magnetization for cosintering with silver or gold metallization.

In this context, the Applicant proposes another solution using a new ferrite material comprising lithium and sintering at less than 920° C. while exhibiting a saturation magnetization greater than 180 mT. This new ferrite material can advantageously be obtained from the addition of so-called “raw” ferrite to calcined (or chamotte) powder before sintering lithium salt as a flux. The melting phase, having a low melting point, helps with sintering.

The lithium salt used can advantageously be, for example, lithium carbonate, its melting point being 723°C.

More specifically, the subject of the present invention is a ferrite material with a garnet structure, characterized in that it corresponds to the following chemical formula:
(Y _a TR _b Bi _b' Fe _c Al _d In _e Ca _f Cu _g Sn _h V _i Co _j Si _k O _12± γ) + x (Li ₂ CO ₃ or Li ₂ O or LiF or LiCl)
with x, in % by weight, between 0.1 and 2;
with TR: a rare earth or a combination of rare earths not comprising the element Y;
-1 ≤ γ ≤ 1;
3 (a+b+b'+c+d+e) + 2 (f+g+j) + 4 (h+k) + 5 i = 24±2γ
0 ≤ a ≤ 2.5;
0 ≤ b ≤ 1.5;
0.5<b'<3;
4 ≤ c ≤ 5;
0≤d≤1.5;
0 ≤ e ≤ 0.8;
0 ≤ f ≤ 1;
0<g≤0.05;
0 < h ≤ 1;
0 ≤ i ≤ 0.8;
0 ≤ d ≤ 0.5;
0 ≤ k ≤ 0.5.

The invention also relates to a component or device comprising the ferrite material according to the invention and metallizations, advantageously in silver. The component or device can be a circulator, an isolator, a switch or a phase shifter.

Another subject of the invention is a process for manufacturing a ferrite material according to the invention, said process comprising:
- the weighing of raw materials such as oxides or carbonates;
- a first grinding of said raw materials;
- a calcining step (also called chamottage) of said ground raw materials at a temperature between 750°C and 850°C making it possible to obtain a raw ferrite material powder;
- a second grinding of said raw ferrite material powder;
- the addition of a flux of lithium salt which can be Li₂CO₃, Li₂O, LiF or LiCl, to said raw ferrite material powder.

The ferrite material resulting from the raw ferrite material powder and the lithium salt flux can advantageously be sintered at a temperature between 850°C and 920°C.

According to variants of the process of the invention, the raw material being Y_2.03That_{0, 25}Bi_0.67Cu_0.05Fe_4.7sn_0.3O₁₂ ,or Y_1.98That_0.3Bi_0.67Cu_0.05Fe_{4, 65}sn_{0, 3 0}O_{12 -}γ, between 0.2 and 0.75% by mass of Li flux is added₂CO_3,the sintering temperature on the resulting assembly being of the order of 850°C to 920°C.

Another subject of the invention is a process for manufacturing a component or device comprising several elements including a ferrite material according to the invention, characterized in that:
- Said ferrite material is prepared according to the method of the invention;
- a sintering operation is carried out during which said ferrite is secured to at least one of said other elements of said component or device, or to a precursor (gold or silver metal, dielectric at low sintering temperature, ferrite at low sintering temperature, etc.) said element by a cosintering process.

In the component or device, at least one of the other elements is a layer of metal and advantageously silver.

The invention will be better understood and other advantages will appear on reading the following description, given on a non-limiting basis and thanks to the appended figures, including:

illustrates the diagram of a three-plate circulator according to the prior art;

illustrates a three-plate circulator according to the known art which can be produced by cosintering;

illustrates a “ microstrip ” microstrip line circulator according to the known art which can be produced by cosintering;

illustrates dielectric loss and permittivity test results of a ferrite material of the invention as a function of frequency expressed in Hertz;

illustrates cosintering test results of a ferrite of the invention with a deposit of silver, after cosintering at 900° C.;

represents a flowchart of the steps of the process for manufacturing a ferrite material according to the invention.

In general, the ferrite material of the invention corresponds to the following chemical formula:
(Y_ToTR_bBi_b'Fe_vsAl_dIn_eThat_fCu_gsn_hV_ICo_IWhether_kO_12±γ) + x (Li₂CO₃or Li₂O or LiF or LiCl)
with x, in % by weight, between 0.1 and 2;
with TR: a rare earth or a combination of rare earths not including the element Y;
-1 ≤ γ ≤ 1;
3 (a+b+b'+c+d+e) + 2 (f+g+j) + 4 (h+k) + 5 i = 24±2γ;
0 ≤ a ≤ 2.5;
0 ≤ b ≤ 1.5;
0.5 ≤ b’ < 3;
4 ≤ c ≤ 5;
0≤d≤1.5;
0 ≤ e ≤ 0.8;
0 ≤ f ≤ 1;
0<g≤0.05;
0 < h ≤ 1;
0 ≤ i ≤ 0.8;
0 ≤ d ≤ 0.5;
0 ≤ k ≤ 0.5.

By this formula, it should be understood that we take x (between 0.1 and 2) grams of Li ₂ CO ₃ (or Li ₂ O or LiF or LiCl) for 100g of ferrite of formulation Y _a TR _{b Bi b '} Fe _c Al _d In _e Ca _f Cu _g Sn _h V _i Co _j Si _k O _12± γ.

Rare earths can be used for the purpose of modifying the saturation magnetization and improving the power handling.

The use of copper and bismuth makes it possible to reduce the sintering temperature.

Bismuth is used for the purpose of increasing the permittivity and lowering the sintering temperature.

Calcium can be used to balance excess loads due to the introduction of zirconium, tin or titanium. It can make it possible to stabilize the mesh in the case of the use of a high level of bismuth for example.

The substitution of iron by aluminum can allow a reduction of the linewidths and a reduction of the magnetization at saturation.

Preferably, the lithium salt added has a mass proportion of between 0.15 and 1.5%, and more preferably between 0.15 and 1.2%, for example 0.75%. This mass proportion depends on the ferrite material. Adding lithium salt lowers the sintering temperature. However, the lithium present in the material can, beyond a certain quantity, generate pollution of the material. The preferred ranges and the example of 0.75% cited make it possible to obtain a good compromise in terms of sintering temperature and properties of the material obtained.

As will appear clearly below, the substitution of iron by tin makes it possible to adapt the magnetization to saturation.

The ferrite materials of the present invention are produced according to a conventional process of ceramic synthesis. The different stages, represented by a flowchart at , are :
- the weighing of the raw materials (step 100);
- the grinding of the mixture previously obtained (step 110);
- a calcination step (step 120), also called chamottage, the purpose of which is to synthesize the garnet phase in powder form and to obtain a powder of so-called raw ferrite material;
- a second grinding step (step 130);
- the introduction of an addition of lithium-based flux (step 140): the addition of flux takes place on the calcined phase (garnet phase formed by heat treatment). It is added to the calcined phase using a mixer (blade mixer, attritor, jar, etc.).

After this flux addition, standard shaping (step 150) and sintering (step 160) steps can be performed. The purpose of sintering the reground chamotte powder at a higher temperature is to densify the ceramic while giving it the desired shape.

The first and the second grinding are advantageously carried out in a humid environment.

The sintering of the reground powder is advantageously carried out under air or under oxygen.

The grinding operations are advantageously carried out with a ball mill and/or by attrition.

The process for manufacturing a ferrite material according to the invention may optionally include an additional calcination step. However, it may be noted that advantageously, the manufacturing process according to the invention may comprise only one calcination step.

Indeed, the materials of the invention are obtained by a conventional process of ceramic synthesis. But the number of steps and therefore the simplicity of the synthesis depends on the material. The insertion of zirconium oxide in the garnet structure is complicated and two calcination steps are necessary to obtain a pure phase. Some impurities may even remain after these two calcinations and be responsible for magnetic and dielectric losses. In the case of the use of tin oxide in the material of the invention, on the other hand, a single calcination may be sufficient to obtain the totally pure phase.

The performances obtained are described below in the context of examples with ferrite materials substituted with tin comprising the use of lithium carbonate as a flux and with ferrite materials substituted with tin not comprising the addition of lithium-based flux.

• Ferrite A : Y_2,03Ca_0,25Bi_0,67Cu_0,05Fe_4,7Sn_0,3O₁₂
• Ferrite B : Y_2,03Ca_0,25Bi_0,67Cu_0,05Fe_4,7Sn_0,3O₁₂+ 0,64% massique Li₂CO₃
• Ferrite C : Y_1,93Ca_0,35Bi_0,67Cu_0,05Fe_4,6Sn_0,4O₁₂
• Ferrite D : Y_1,93Ca_0,35Bi_0,67Cu_0,05Fe_4,6Sn_0,4O₁₂+ 0,64% massique Li₂CO₃
• Ferrite E : Y_1,83Ca_0,45Bi_0,67Cu_0,05Fe_4,5Sn_0,5O₁₂
• Ferrite F : Y_1,83Ca_0,45Bi_0,67Cu_0,05Fe_4,5Sn_0,5O₁₂+ 0,64% massique Li₂CO₃

In order to highlight the effects of the use of tin and lithium carbonate, different compositions were studied:

• Ferrite A: Y _2.03 Ca _0.25 Bi _0.67 Cu _0.05 Fe _4.7 Sn _0.3 O ₁₂
• Ferrite B: Y _2.03 Ca _0.25 Bi _0.67 Cu _0.05 Fe _4.7 Sn _0.3 O ₁₂ + 0.64% by weight Li ₂ CO ₃
• Ferrite C: Y _1.93 Ca _0.35 Bi _0.67 Cu _0.05 Fe _4.6 Sn _0.4 O ₁₂
• Ferrite D: Y _1.93 Ca _0.35 Bi _0.67 Cu _0.05 Fe _4.6 Sn _0.4 O ₁₂ + 0.64% by mass Li ₂ CO ₃
• Ferrite E: Y _1.83 Ca _0.45 Bi _0.67 Cu _0.05 Fe _4.5 Sn _0.5 O ₁₂
• Ferrite F: Y _1.83 Ca _0.45 Bi _0.67 Cu _0.05 Fe _4.5 Sn _0.5 O ₁₂ + 0.64% by mass Li ₂ CO ₃

The first characterization is the verification of phase formation by X-ray diffraction. This measurement confirms good phase formation.

First, material shrinkages were observed for sintering at 900°C. In order to have a reasonable density, the expected shrinkage value is 16-17%. Material % withdrawal Densities (g/cm ³ ) Ferrite A 0 - Ferrite B 17.1 5.32 Ferrite C 0 - D-ferrite 16.1 5.25 E-ferrite 0 - F-ferrite 16.8 5.21

The impact of lithium carbonate on densification is clear: the shrinkage, non-existent in its absence, increases to more than 16% when lithium carbonate is added as a melt on the phase already formed. The lithium carbonate therefore allows an improvement in the densification. It remains to verify that the saturation magnetization is not impacted as in the case of substitutions of iron by zirconium, titanium or hafnium.

The saturation magnetizations of the materials substituted Sn and with addition of lithium carbonate are presented in the table below. Material Magnetization at saturation (mT) Ferrite B 192 D-ferrite 178 F-ferrite 169

These results show that the tin-substituted ferrite B material comprising the use of lithium carbonate according to the invention has a saturation magnetization greater than 190 mT.

There illustrates test results of the dielectric losses (tan δ) and the permittivity (ε) of a ferrite material of the invention as a function of the frequency expressed in Hertz. The dielectric losses were measured. The results are presented for the material ferrite B, which has a saturation magnetization greater than 190 mT.

Curve C1 represents the permittivity with a sintering temperature of 900°C. Curve C2 represents the permittivity with a sintering temperature of 900°C and an annealing at 925°C. Curve C3 represents the dielectric losses with a sintering temperature of 900°C. Curve C4 represents the dielectric losses with a sintering temperature of 900°C and an annealing at 925°C. We see that the permittivity remains high, around 21 and the losses are on the other hand a little high at low frequency (tan δ of the order of 5.10 ^-2 ). A second annealing was therefore carried out, it allows a decrease in the relaxation: the permittivity remains the same, but the losses decrease (tan δ of the order of 3.10 ^-2 ).

Dielectric losses were also measured at 9.2 GHz (waveguide measurement). The results are as follows: ε = 21 and tan δ = 7.10 ^-4 .

These values are quite satisfactory for the application: the permittivity remains high for a garnet and the losses are very low.

There illustrates cosintering test results of a ferrite of the invention with a deposit of silver, after cosintering at 900°C. Cosintering tests confirm the compatibility of the material according to the invention with silver. A layer of silver was deposited using a screen printing screen and then the assembly was co-sintered at 900°C. The images shown at the present the results obtained.

These cosintering tests are quite conclusive. Indeed, after sintering the ferrite pellet and the metallization at 900°C, the quality of the silver layer is not altered and no diffusion is observed.

The direct application of the present invention is the production of circulators and insulators using LTCC technology (Low Temperature Cofired Ceramics) or other additive technology. The present invention makes it possible to simplify complex assemblies thanks to cosintering: the number of production steps is reduced. In addition, it is possible to dispense with the use of glues which degrade the properties and which make it a less durable technology.

It is also recalled that it was not possible, until now, to cosinter a garnet structure ferrite with high saturation magnetization (for applications in Ku band circulators for example) with silver ( sintering temperature or silver compatibility issue). The present invention makes it possible to cosinter silver with a ferrite of garnet structure having a saturation magnetization greater than 180 mT.

Thus, the invention is based on the substitution of the iron ions of the garnet phase by tin ions combined with the use of lithium carbonate or lithium oxide as a flux. While the known substitutions of the prior art indicated that the increase in saturation magnetization is to the detriment of the sintering temperature, and vice versa, the two characteristics combined together according to the invention make it possible to obtain a ferrite of garnet structure compatible for co-sintering with silver and possessing a sufficiently high saturation magnetization.

Claims (9)

Ferrite material with a garnet structure, characterized in that it has the following chemical formula:
(Y_ToTR_bBi_b'Fe_vsAl_dIn_eThat_fCu_gsn_hV_ICo_IWhether_kO_12±γ) + x (Li₂CO₃or Li₂O or LiF or LiCl)
with x, in % by weight, between 0.1 and 2;
with TR: a rare earth or a combination of rare earths not including the element Y;
-1 ≤ γ ≤ 1;
3 (a+b+b'+c+d+e) + 2 (f+g+j) + 4 (h+k) + 5 i = 24±2γ;
0 ≤ a ≤ 2.5;
0 ≤ b ≤ 1.5;
0.5 ≤ b’ < 3;
4 ≤ c ≤ 5;
0≤d≤1.5;
0 ≤ e ≤ 0.8;
0 ≤ f ≤ 1;
0<g≤0.05;
0 < h ≤ 1;
0 ≤ i ≤ 0.8;
0 ≤ d ≤ 0.5;
0 ≤ k ≤ 0.5. Device comprising the ferrite material according to claim 1 and metallizations, the metallizations preferably being in silver. Circulator comprising the ferrite material according to claim 1 and metallizations, the metallizations preferably being in silver. Insulator comprising the ferrite material according to claim 1 and metallizations, the metallizations preferably being in silver. A method of manufacturing a ferrite material according to claim 1, said method comprising:
- a step of weighing (step 100) raw materials of the oxide or carbonate type;
- a first grinding (step 110) of said raw materials;
- a calcining step (step 120) of said ground raw materials at a temperature of between 750° C. and 800° C. making it possible to obtain the raw ferrite material;
- a second grinding (step 130) of said raw ferrite material powder;
- a step of adding (step 140) a lithium salt flux from among Li ₂ CO ₃ , Li ₂ O, LiF or LiCl, to said raw ferrite material powder. A method of manufacturing a ferrite material according to claim 5, wherein:
- the raw ferrite material being Y_2.03That_0.25Bi_0.67Cu_0.05Fe_4.7sn_0.3O₁₂ or Y_1.98That_0.3Bi_0.67Cu_0.05Fe_4.65sn_0.30O_12-γ ;
- between 0.2 and 0.75% by weight of Li flux is added₂CO_3. Method of manufacturing a device comprising several elements including a ferrite material according to claim 1, characterized in that:
- Said ferrite material is prepared by the method according to one of claims 5 or 6;
- A sintering operation is carried out during which said ferrite material is secured to at least one of said other elements of said device, or to a precursor of said element by a cosintering process. Method of manufacturing a device, according to claim 7, characterized in that at least one of the other elements is a layer of metal. Method of manufacturing a device, according to claim 8, characterized in that the metal is silver.